Abstract:

An electrostatic precipitator for removing a particulate material includes
a housing having an internally formed air path communicating between an
inlet for drawing polluted air containing particulate material and an air
outlet for emitting clean air purified by removing the particulate
material, an air stream generating means that generates an air stream, a
discharging means that charges the particulate material, and a collection
device provided in the air stream to collect the particulate material
which has been charged by the discharging means. The collection device
includes a collection belt including a flat wire belt defining a
three-dimensional collection surface. The precipitator further includes a
brush and vacuum assembly for removing the particulate material and
reducing the risk of reentrainment in the air stream.

Claims:

1. An electrostatic precipitator for removing a particulate material,
comprising:a housing having an internally formed air path communicating
between an inlet for drawing polluted air containing particulate material
and an air outlet for emitting clean air purified by removing the
particulate material;an air stream generating means that generates an air
stream;a discharging means that charges the particulate material;a
collection device provided in the air stream to collect the particulate
material which has been charged by the discharging means, said collection
device including a collection belt;wherein said collection belt comprises
a flat wire belt defining a three-dimensional collection surface.

2. The electrostatic precipitator according to claim 1, further comprising
a brush and vacuum assembly for removing the particulate material and
reducing the risk of reentrainment in the air stream.

3. The electrostatic precipitator according to claim 2, wherein said brush
comprises a rotary brush.

4. The electrostatic precipitator according to claim 3, wherein said
rotary brush is stationary.

5. The electrostatic precipitator according to claim 3, wherein said
rotary brush is rotatable.

6. The electrostatic precipitator according to claim 1, wherein said
discharging means comprises a plurality of electrodes.

7. The electrostatic precipitator according to claim 1, wherein said
discharging means comprises at least one high voltage line.

8. The electrostatic precipitator according to claim 1, wherein said flat
wire belt comprises a plurality of spaced tractive rods and a plurality
of rows of wickets interconnecting said plurality of spaced tractive
rods.

9. The electrostatic precipitator according to claim 8, wherein each said
row of wickets includes a plurality of links.

10. The electrostatic precipitator according to claim 9, wherein said
plurality of links have a depth between 0.188''-0.500'', thereby defining
said three-dimensional collection surface.

11. The electrostatic precipitator according to claim 1, wherein said
collection belt is continuously rotatable about opposed sprockets.

12. The electrostatic precipitator according to claim 11, wherein said
opposed sprockets are mounted on opposing shafts.

13. A collection device for use in an electrostatic precipitator in which
particulate material entrained in an air stream has been charged, said
collection device comprising:a continuously rotatable collection belt,
said collection belt comprising a flat wire belt defining a
three-dimensional collection surface.

14. The collection device according to claim 13, wherein said flat wire
belt comprises a plurality of spaced tractive rods and a plurality of
rows of wickets interconnecting said plurality of spaced tractive rods.

15. The collection device according to claim 14, wherein each said row of
wickets includes a plurality of links.

16. The collection device according to claim 15, wherein said plurality of
links have a predetermined depth, thereby defining said three-dimensional
collection surface.

17. The collection device according to claim 13, further comprising a
brush and vacuum assembly for removing the particulate material and
reducing the risk of reentrainment in the air stream.

18. The collection device according to claim 17, wherein said brush
comprises a rotary brush.

19. The collection device according to claim 17, wherein said rotary brush
is stationary.

20. The collection device according to claim 17, wherein said rotary brush
is rotatable.

Description:

TECHNICAL FIELD

[0001]The present invention relates to an electrostatic precipitator, more
particularly an electrostatic precipitator capable of collecting an
electrically charged fine particulate by using a moving collection
surface, and still more particularly, a plurality of moving
three-dimensional collection elements.

BACKGROUND

[0002]Conventionally, before emitting so-called "industrial waste gases",
such as exhaust gases of boilers in factories and smoke from power
generating plants, into the atmosphere, air purification processing is
performed to remove various types of fine particulates contained in the
industrial waste gases, such as mist and dust containing, for example,
powders containing oil, moisture, and/or the like, which can pollutes the
atmosphere. Direct emission of the industrial waste gases containing the
fine particulate into the atmosphere significantly affects the global
environment, so that there are cases where it is obligatory to perform
collection thereof by standards of a national or local governments. Dust
collection is one of several purification techniques used to collect fine
particles contained in polluted air.

[0003]The dust collection principle of electrostatic dust precipitators is
such that electric charges are supplied to the fine particulate through
corona discharges generated from discharge electrodes, and coulomb forces
are used to electrostatically attract the charged fine particulate onto
collector electrodes which are opposed electrodes, whereby the fine
particulate is collected. An electrostatic precipitator has significant
advantages, such as: 1) the pressure loss is small; 2) a large amount of
gases can be processed; and 3) the collection efficiency is high.
Therefore, electrostatic precipitators are commonly used in such
environments as factories and power generating plants which emit a large
amount of polluted air.

[0004]Generally, the construction of an electrostatic precipitator
includes discharge electrodes each formed into a shape having a large
surface curvature, such as a needle or wire material, for generating
corona discharges for supplying electric charges to the fine particulate;
collector electrodes, as opposed electrodes, each formed into a flat
plate for collecting the charged fine particulate; a rectifier unit for
rectifying the flow of gas streams in the electrostatic dust
precipitator; a dust removal device for separating deposited fine
particulate from the collector electrodes; a hopper for collecting the
separated fine particulate; and a power system and electric charge
control device to cause corona discharges. In using the dust removal unit
of a electrostatic precipitator, the collector electrodes are rapped by a
hammer or the like to dislodge collected fine particulate therefrom and
collect the fine particulate in a collection unit, such as a hopper,
provided in a lower portion. When a large amount of the fine particulate
is collected onto the collector electrodes, the coulomb force for
attracting the charged fine particulate may be reduced, thereby reducing
the collection efficiency. Therefore, dust removal units are important in
order to remove a build up of the fine particulate from the collector
plates.

[0005]However, the cleaning of the collection plates of the prior art
systems presents a serious problem inasmuch as a substantial amount of
reentrainment of the dust occurs. Because of the proximity of the plates
to the gas flow channel, some of the dust particles dislodged during the
rapping process are reintroduced into the gas stream. The reentrained
particles must then be recharged and again collected for effective
removal from the gas stream.

[0006]Prior attempts to increase the efficiency of the prior art systems
have included the use of additional collection plates in the gas flow
channel to increase the surface area available for deposition of the
dust. Although producing some increase in efficiency and length of
operating times between cleanings, this approach results in significant
increases in the overall size and complexity of the precipitation systems
and is therefore not entirely satisfactory.

[0007]Precipitators have also been proposed in which the particle
collection surfaces are in the form of endless belts that continuously
move through the collection zone. For example, in the U.S. Pat. No.
2,579,440 to Palmer, the contents of which are hereby incorporated by
reference, dust particles are collected on a moving belt that has been
charged to a polarity opposite to that imparted to the dust particles and
are removed from the belt surfaces at a point remote from the gas stream.
Such apparatus is, however, subject to the disadvantage that the charges
applied to the surfaces of the belts are susceptible of being pulled off
the belts by the charged dust particles. When this occurs, the particular
dust particles affected are not removed from the gas stream and, in
addition, the precipitation field is weakened because the charge carried
by the belts is reduced.

[0008]It is an object of this invention to enhance electrostatic
precipitation efficiency by combining an improved collection surface in
which the electrostatic field forces acting on the deposited particles
are strong enough throughout the collection surface to capture and retain
the particles, and an improved dust collection system which reduces the
incidence of particle reentrainment.

SUMMARY

[0009]These and other objects of the invention are provided by providing
an electrostatic precipitator including a housing having an internally
formed air path communicating between an inlet for drawing polluted air
containing particulate material and an air outlet for emitting clean air
purified by removing the particulate material. An air stream generating
means generates the air stream and a discharging means is provided for
charging the particulate material. A collection device is provided in the
air stream to collect the particulate material which has been charged by
the discharging means. The collection device includes a collection belt
which continuously rotates about opposed sprockets, the collection belt
preferably comprising a flat wire belt defining a three-dimensional
collection surface. The electrostatic precipitator further includes a
brush and vacuum assembly for removing the collected particulate while
reducing the risk of reentrainment in the air stream.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0010]These and other objects, features, and advantages of the present
invention will become more readily apparent to those skilled in the art
upon reading the following detailed description, in conjunction with the
appended drawings in which:

[0011]FIG. 1 is a perspective view of an electrostatic precipitator
according to a preferred embodiment of the invention.

[0012]FIG. 2 is a perspective view of the cleaning system for the
collection belt shown in FIG. 1.

[0013]FIG. 3 is an enlarged fragmentary perspective view of the collection
belt shown in FIG. 1.

DETAILED DESCRIPTION

[0014]The collection surface for an electrostatic precipitator 10 in
accordance with a preferred embodiment of the invention includes a
collection belt 100 driven about an array of sprockets 110 arranged on a
shaft 114 at either the top and/or the bottom of the device, as shown
generally in FIG. 1. The moving collection belt is designed as a
continuous loop so as to maximize the available collection surface area
while minimizing pressure drop. Collection belt 100 preferably comprises
a flat wire conveyor belt, as described more fully in U.S. Patent
Publication No. 2007/0080048, the contents of which are hereby
incorporated by reference.

[0015]Referring also to FIG. 3, belt 100 includes a plurality of spaced
tractive rods 180 disposed in succession and transversely with respect to
a direction of travel, each rod 180 having two ends 205 and 207. Belt 100
further includes a plurality of rows of wickets 160 transversely disposed
with respect to the direction of travel, and interconnecting the
succession of rods 180. Each row of wickets 160 is comprised of a
plurality of links 170, each link connecting a rod 180 with a following
rod in the succession. In addition, belt 100 preferably includes at least
one row of edge links 140 disposed along each edge 120, 130 of the
collection belt for engagement with the sprockets 110. Depending upon the
particular application, belt 100 may also be manufactured with several
rows of links 150 disposed between edge links 140 for engagement with
center sprockets 112, as shown in FIG. 1. Unlike collection plates or
rubber belts used in conventional electrostatic precipitators, which
present a substantially two-dimensional surface for collection, the use
of belt 100 provides a three-dimensional collection surface area. That
is, each wicket 160 has a depth "d" defining the thickness of the wicket
and ranging from approximately 0.188'' to approximately 0.500''.

[0016]The electrostatic precipitator 10 further includes discharging means
such as electrodes or high voltage lines 190 for charging the particulate
material entrained in the air flow "A" passing through the precipitator
housing 12 by way of air inlet 14 and air outlet 16. The air flow is
preferably created by an air stream generator (not shown). The material
for the collection belt 100 is selected based upon its ability to serve
as a proper ground, examples of which include stainless and carbon
steels. The collection belt 100 is preferably grounded through contact
with the sprockets 110, 112 which are attached to grounded shaft 114.
Thus, the charged particles entrained in air flow "A" are collected on
the surface of collection belt 100 as the air flow passes through
precipitator 10. The collection belt 100 can also be grounded via a
contact brush (not shown).

[0017]In order to remove the particulate material that is collected on
belt 100, the invention further provides a rotary brush and/or linear
brush vacuum system 200, as shown more clearly in FIG. 2. More
particularly, as the collection belt 100 is moving, a rotary brush 210 is
preferably provided to engage the belt surface and dislodge the collected
particulate material thereon. The rotary brush 210 may be stationary or
powered to rotate either with or opposite to the direction of travel of
belt 100. One skilled in the art will appreciate that a linear brush or
any other type of brush device could also be used for the same purpose.
In order to avoid the particulate material from becoming reentrained in
the air flow, a vacuum nozzle 220 is provided in close proximity to the
brush 210. Hence, any particles dislodged by the rotary brush 210 are
immediately removed by the vacuum system 200. Thus, the present invention
reduces the amount of particulate material that will be reentrained in
the air stream and it avoids the need for interrupting the electrostatic
precipitator in order to empty a hopper or otherwise remove particles
that have been collected due to the self-cleaning nature of the brush and
vacuum system 200. The electrostatic precipitator according to the
invention can thus be continuously cleaned without affecting the
performance of the precipitator.

[0018]Although certain preferred embodiments of the present invention have
been shown and described in detail, it should be understood that various
changes and modifications may be made therein without departing from the
scope of the appended claims.